349 



I. 



TABLES 



FOR 



DETERMINING DIFFERENCES OF LEVEL BY MEANS OF 

 BAROMETRICAL OBSERVATIONS, 



COMPUTED FROM THE COMPLETE FORMULA OF LAPLACE, 



By M. T. Delcros. 



Construction of the TaUes. 



If we take z = difference of level of the two barometers, 

 a = earth's mean radius = 6366200 metres, 

 L = mean latitude between the two stations, 



and further : — , , . , r xu u 



r h = observed height of the barometer, 



r Lower. S T = temperature of the barometer, 



C t = temperature of the air, 



At Station. <| ( h' = observed height of the barometer, 



Upper. ^ T' = temperature of the barometer, 



C t' = temperature of the air, 



('P 'p/\ 



we shall have, according to Laplace, the following general and complete equation 



, = 18336 metres X 1 ( 1 + 0.0028371 cos. 2. L) 



[ ((1 + ^). Log. (A) +^0.868589) 



after the proper transformations this equation becomes : — 



z = Log. (4) 1®3^^ "^^^^^^ ^ 



D 



1 ( 1 -1-0.0028371 COS. 2. L) 



(log^)j:^68589)J-\ 



Log. (4") / 



9 



i( 



1 + 



